1. Field of the Invention
The present invention relates to an image formation device, a display screen switching method, and a program. The present invention more specifically relates to a technique of controlling switching of a display screen to be displayed on a display unit capable of displaying various types of information.
2. Description of the Background Art
Publicly known conventional control methods of switching a display screen of a computer include such a technique as is introduced for example in Japanese Patent Application Laid-Open No. 2001-222406. According to this technique, a single operating system (OS) can simultaneously activate a plurality of windows, and a window is switched according to a user's input command, or by automatically interposing an active window. In this technique, an operating system that activates a plurality of windows determines which window should be active, and then a display screen is switched based on the determination.
Further, publicly known conventional methods of switching a window in a device with a multi-window display function include such a technique as is introduced for example in Japanese Patent Application Laid-Open No. 63-45628 (1988). According to this technique, a transition rule for causing a right to possess an input device to make a transition between windows is recorded. When an input is received from the input device, the right of possession is transferred to a next window according to the transition rule, thereby switching a window. For switching of a window, this technique requires the transition rule for switching a window to be stored in advance.
Image formation devices called by a name such as complex devices or MFPs (multifunction peripherals) have several functions including a copy function, a scan function, a print function and others. In recent years, there is a trend toward an increasing number of functions implemented in the image formation devices. In this situation, a user who uses an image formation device does not necessarily require all functions implemented in the image formation device. So, this type of image formation device has basic functions including a copy function, a scan function, a print function and others as standard functions implemented in advance therein. Another function may be added as an extended function to the image formation device.
This image formation device has an operating system for controlling hardware sections including a scanner section, a printer section and others. Functions such as a copy function or a scan function are each implemented as an application program. As these application programs are started by the operating system, the corresponding functions are become available in the image formation device. So, in order to add an extended function to the image formation device, an application program corresponding to this extended function should be installed in the image formation device.
When the extended function is added to image formation device, a display screen that can be displayed on an operational panel of the image formation device includes a display screen relating to standard functions, and a display screen relating to the added extended function. In the conventional image formation device, an operating system controls switching among these display screens.
However, if an operating system always makes a determination as to switching of a display screen to be displayed on an operational panel of the above-described image formation device in which an application program corresponding to an extended function can be installed, a burden on the operating system may increase. As an example, while the added extended function is in operation in the image formation device, and a display screen relating to this extended function is displayed on the operational panel, the operating system may detect generation of an error in a scanner section or in a printer section. In this case, in order for the operating system to appropriately determine whether or not a display screen to be displayed on the operational panel should be switched to an error screen, the operating system should precisely figure out the substance of processing of the extended function. So, a function to figure out the substance of processing of the extended function to be added later should be incorporated in advance in the operating system. This also increases a burden on the operating system.
Meanwhile, when generation of an error in the scanner section or in the printer section is detected during the operation of the extended function, the operating system may forcibly switch a display screen on the operational panel to the error screen without any consideration of the substance of processing of the extended function. This may reduce the increase of burden on the operating system. In this case, however, the display screen on the operational panel is forcibly switched to the error screen even if the extended function is not affected continuance of its operation by the error generated in the scanner section or in the printer section. So, a user who uses the extended function confronts the unnecessary screen switching that was forcibly made, resulting in the reduction in operability of the extended function.
Besides, a recent image formation device can make access to an external server such as a Web server through a network, so that a display screen created in the external server can be displayed on an operational panel of the image formation device. In this case, the display screen created in the external server can be displayed as an operation screen when a user uses a standard function or an extended function of the image formation device. So, the user is allowed to adapt the design of a display screen at the user's choice and make the operational panel displaying the same, for example, by modifying a display screen created in the external server with operation keys of colorful designs and the like.
However, the external server is not necessarily a reliable device provided by a manufacturer of the image formation device. So, there arises a problem concerning the reliability of a display screen created in the external server.
This problem becomes a serious issue especially when an error is generated in the image formation device. As an example, when an error screen created in the external server does not suitably provide the precise details of the error or a way to handle the error, a user cannot take appropriate actions against the error. As a result, the error in the image formation device remains for a long time before it is eliminated, causing the deterioration of the reliability of the image formation device itself. In order to avoid this, each time an error is generated in the image formation device, a display screen to be displayed on an operational panel may forcibly be switched to an error screen created in the image formation device. In this case, however, a display screen is switched to the error screen created in the image formation device even when the error is a minor error such as shortage of sheets. This causes a change in the design of a display screen, so uniformity in the screen design is broken.
In addition, when a display screen created in the external server is displayed on the operational panel, the external server cannot recognize an extended function added to the image formation device, the particulars of other specifications or the like. So, if a display screen created in the external server is displayed on the operational panel as it is, sometimes an item that cannot be set in the image formation device is shown to be settable, or sometimes a combination of two or more items which cannot be set simultaneously in the image formation device is shown to be available as a target of simultaneous setting. These also lead a problem that reduces operability for a user to operate the image formation device.